Deep neural network-enabled battery open-circuit voltage estimation based on partial charging data

Battery management systems(BMSs) play a vital role in ensuring efficient and reliable operations of lithium-ion batteries.The main function of the BMSs is to estimate battery states and diagnose battery health using battery open-circuit voltage(OCV).However,acquiring the complete OCV data online can be a challenging endeavor due to the time-consuming measurement process or the need for specific operating conditions required by OCV estimation models.In addressing these concerns,this study introduces a deep neural network-combined framework for accurate and robust OCV estimation,utilizing partial daily charging data.We incorporate a generative deep learning model to extract aging-related features from data and generate high-fidelity OCV curves.Correlation analysis is employed to identify the optimal partial charging data,optimizing the OCV estimation precision while preserving exceptional flexibility.The validation results,using data from nickel-cobalt-magnesium(NCM) batteries,illustrate the accurate estimation of the complete OCV-capacity curve,with an average root mean square errors(RMSE) of less than 3 mAh.Achieving this level of precision for OCV estimation requires only around 50 s collection of partial charging data.Further validations on diverse battery types operating under various conditions confirm the effectiveness of our proposed method.Additional cases of precise health diagnosis based on OCV highlight the significance of conducting online OCV estimation.Our method provides a flexible approach to achieve complete OCV estimation and holds promise for generalization to other tasks in BMSs.

Understanding the correlation between energy-state mismatching and open-circuit voltage loss in bulk heterojunction solar cells

Photoinduced intermolecular charge transfer(PICT)determines the voltage loss in bulk heterojunction(BHJ)organic photovoltaics(OPVs),and this voltage loss can be minimized by inducing efficient PICT,which requires energy-state matching between the donor and acceptor at the BHJ interfaces.Thus,both geometrically and energetically accessible delocalized state matching at the hot energy level is crucial for achieving efficient PICT.In this study,an effective method for quantifying the hot state matching of OPVs was developed.The degree of energy-state matching between the electron donor and acceptor at BHJ interfaces was quantified using a mismatching factor(MF)calculated from the modified optical density of the BHJ.Furthermore,the correlation between the open-circuit voltage(Voc)of the OPV device and energy-state matching at the BHJ interface was investigated using the calculated MF.The OPVs with small absolute MF values exhibited high Voc values.This result clearly indicates that the energy-state matching between the donor and acceptor is crucial for achieving a high Voc in OPVs.Because the MF indicates the degree of energy-state matching,which is a critical factor for suppressing energy loss,it can be used to estimate the Voc loss in OPVs.

Open-circuit voltage analysis of p-i-n type amorphous silicon solar cells deposited at low temperature

This paper identifies the contributions of p-a-SiC：H layers and i-a-Si：H layers to the open circuit voltage of p-i-n type a-Si：H solar cells deposited at a low temperature of 125℃. We find that poor quality p-a-SiC：H films under regular conditions lead to a restriction of open circuit voltage although the band gap of the i-layer varies widely. A significant improvement in open circuit voltage has been obtained by using high quality p-~SiC：H films optimized at the ＂low-power regime＂ under low silane flow rates and high hydrogen dilution conditions.

Perovskite Self-Passivation with PCBM for Small Open-Circuit Voltage Loss

It is well known that [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is a common n-type passivation material in PSCs, usually used as an interface modification layer. However, PCBM is extremely expensive and is not suitable for future industrialization. Herein, the various concentrations of PCBM as an additive are adopted for PSCs. It not only avoids the routine process of spin coating the multi-layer films, but also reduces the PCBM material and cost. Meanwhile, PCBM can passivate the grain surface and modulate morphology of perovskite films. Furthermore, the most important optical parameters of solar cells, the current density (Jsc), fill factor (FF), open-circuit voltage (Voc) and power conversion efficiencies (PCE) were improved. Especially, when the PCBM doping ratio in CH3NH3PbI3 (MAPbI3) precursor solution was 1 wt%, the device obtained the smallest Voc decay (less than 1%) in the p-i-n type PSCs with poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) as hole transport layer (HTL) and fullerene (C60) as electron transport layer (ETL). The PSCs Voc stability improvement is attributed to enhanced crystallinity of photoactive layer and decreased non-radiative recombination by PCBM doping in the perovskites.

An analytical model to explore open-circuit voltage of a-Si:H/c-Si heterojunction solar cells

The effect of the parameters on the open-circuit voltage, V_(OC) of a-Si:H/c-Si heterojunction solar cells was explored by an analytical model. The analytical results show that V_(OC) increases linearly with the logarithm of illumination intensity under usual illumination. There are two critical values of the interface state density(D_(it)) for the open-circuit voltage(V_(OC)), D_(it)^(crit,1) and D_(it)crit,2(a few 1010 cm^(-2)·e V^(-1)). V_(OC) decreases remarkably when D_(it) is higher than D_(it)^(crit,1). To achieve high V_(OC), the interface states should reduce down to a few 1010 cm^(-2)·e V^(-1). Due to the difference between the effective density of states in the conduction and valence band edges of c-Si, the open-circuit voltage of a-Si:H/c-Si heterojunction cells fabricated on n-type c-Si wafers is about 22 mV higher than that fabricated on p-type c-Si wafers at the same case. V_(OC) decreases with decreasing the a-Si:H doping concentration at low doping level since the electric field over the c-Si depletion region is reduced at low doping level. Therefore, the a-Si:H layer should be doped higher than a critical value of 5×10^(18) cm^(-3) to achieve high V_(OC).

Improvement of Open-Circuit Voltage in Organic Photovoltaic Cells with Chemically Modified Indium-Tin Oxide

The possibility of the increase in open-circuit voltage of organic photovoltaic cells based primarily indium-tin oxide (ITO)/rubrene/fullerene/Al structure by changing the work function of ITO anodes and Al cathodes was described in this work. To change built-in potential preferably in order to increase the open-circuit voltage, the work function of ITO should be increased and work function of Al should be decreased. The correlation between the change in work functions of electrodes and performance of the organic photovoltaic cells before and after surface modifications was examined in detail. The enhancement of open-circuit voltage depends on a function of work function change of both ITO and Al electrode. We could show that the built-in potential in the cells played an important role in open-circuit voltage.

Reveal the large open-circuit voltage deficit of all-inorganic CsPbIBr_(2) perovskite solar cells

Due to excellent thermal stability and optoelectronic properties, all-inorganic perovskite is one of the promising candidates to solve the thermal decomposition problem of conventional organic–inorganic hybrid perovskite solar cells(PSCs),but the larger voltage loss(V_(loss)) cannot be ignored, especially CsPbIBr_(2), which limits the improvement of efficiency. To reduce V_(loss), one promising solution is the modification of the energy level alignment between the perovskite layer and adjacent charge transport layer(CTL), which can facilitate charge extraction and reduce carrier recombination rate at the perovskite/CTL interface. Therefore, the key issues of minimum V_(loss) and high efficiency of CsPbIBr_(2)-based PSCs were studied in terms of the perovskite layer thickness, the effects of band offset of the CTL/perovskite layer, the doping concentration of the CTL, and the electrode work function in this study based on device simulations. The open-circuit voltage(V_(oc)) is increased from 1.37 V to 1.52 V by replacing SnO_(2) with ZnO as the electron transport layer(ETL) due to more matching conduction band with the CsPbIBr;layer.

Efficient wide-bandgap perovskite solar cells with open-circuit voltage deficit below 0.4 V via hole-selective interface engineering

Wide-bandgap mixed-halide perovskite solar cells(WBG-PSCs)are promising top cells for efficient tandem photovoltaics to achieve high power conversion efficiency(PCE)at low cost.However,the open-circuit voltage(V_(OC))of WBG-PSCs is still unsatisfactory as the V_(OC)-deficit is generally larger than 0.45 V.Herein,we report a buried interface engineering strategy that substantially improves the V_(OC)of WBG-PSCs by inserting amphiphilic molecular hole-selective materials featuring with a cyanovinyl phosphonic acid(CPA)anchoring group between the perovskite and substrate.The assembly and redistribution of CPA-based amphiphilic molecules at the perovskite-substrate buried interface not only promotes the growth of a low-defect crystalline perovskite thin film,but also suppresses the photo-induced halide phase separation.The energy level alignment between wide-bandgap perovskite and the hole-selective layer is further improved by modulating the substituents on the triphenylamine donor moiety(methoxyls for MPA-CPA,methyls for Me PA-CPA,and bare TPA-CPA).Using a 1.68 e V bandgap perovskite,the Me PA-CPA-based devices achieved an unprecedentedly high V_(OC)of 1.29 V and PCE of 22.3%under standard AM 1.5 sunlight.The V_(OC)-deficit(<0.40 V)is the lowest value reported for WBG-PSCs.This work not only provides an effective approach to decreasing the V_(OC)-deficit of WBG-PSCs,but also confirms the importance of energy level alignment at the charge-selective layers in PSCs.

Sulfolane‑Based Flame‑Retardant Electrolyte for High‑Voltage Sodium‑Ion Batteries

Sodium-ion batteries hold great promise as next-generation energy storage systems.However,the high instability of the electrode/electrolyte interphase during cycling has seriously hindered the development of SIBs.In particular,an unstable cathode–electrolyte interphase(CEI)leads to successive electrolyte side reactions,transition metal leaching and rapid capacity decay,which tends to be exacerbated under high-voltage conditions.Therefore,constructing dense and stable CEIs are crucial for high-performance SIBs.This work reports localized high-concentration electrolyte by incorporating a highly oxidation-resistant sulfolane solvent with non-solvent diluent 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether,which exhibited excellent oxidative stability and was able to form thin,dense and homogeneous CEI.The excellent CEI enabled the O3-type layered oxide cathode NaNi_(1/3)Mn_(1/3)Fe_(1/3)O_(2)(NaNMF)to achieve stable cycling,with a capacity retention of 79.48%after 300 cycles at 1 C and 81.15%after 400 cycles at 2 C with a high charging voltage of 4.2 V.In addition,its nonflammable nature enhances the safety of SIBs.This work provides a viable pathway for the application of sulfolane-based electrolytes on SIBs and the design of next-generation high-voltage electrolytes.

A Novel Thiophene Derivative-based Conjugated Polymer for Polymer Solar Cells with High Open-circuit Voltage

A novel D-A alternative conjugated polymer PBDTDMCT containing benzo[1,2-b：4,5-b＇]dithiophene （BDT） and dimethyl thiophene-3,4-dicarboxylate （DMCT）, was designed and synthesized by Stille cross-coupling reaction. The copolymer exhibited excellent solubility and good thermal stability. The optical band gap determined from the onset of absorption of the polymer film was 2.10 eV. By incorporation of the ester groups into the polymer side chain, the HOMO level of polymer PBDTDMT was tuned to be deep-lying （--5.65 eV）. Open-circuit voltage of polymer solar cells constructed based on PBDTDMT and [6,6]-phenyl-CTwbutyric acid methyl ester （PCTIBM） can be tuned to achieve values as high as ca. 1.0 V.

Work function engineering to enhance open-circuit voltage in planar perovskite solar cells by g-C_(3)N_(4) nanosheets

Enhancement of open-circuit voltage(Voc)is an effective way to improve power conversion efficiency(PCE)of the perovskite solar cells(PSCs).Theoretically,work function engineering of TiO2 electron transport layer can reduce both the loss of Voc and current hysteresis in PSCs.In this work,two-dimensional g-C_(3)N_(4) nanosheets were adopted to modify the compact TiO2 layers in planar PSCs,which can finely tune the work function(WF)and further improve the energy level alignment at the interface to enhance the Voc and diminish the hysteresis.Meanwhile,the quality of perovskite films and charge transfer of the devices were improved by g-C_(3)N_(4) nanosheets.Therefore,the PCE of the planar PSCs was champed to 19.55%without obvious hysteresis compared with the initial 15.81%,mainly owing to the remarkable improvement of VOC from 1.01 to 1.11 V.In addition,the stability of the devices was obviously improved.The results demonstrate an effective strategy of W_(F) engineering to enhance Voc and diminish hysteresis phenomenon for improving the performance of PSCs.

Large photovoltaic effect with ultrahigh open-circuit voltage in relaxor-based ferroelectric Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)ceramics

Recently,the anomalous photovoltaic effect of ferroelectric materials has attracted considerable attention in the construction of efficient solar cells owing to the above-bandgap photovoltage of these materials.In this study,we investigate the anomalous photovoltaic effect of relaxor-based ferroelectric Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PIMN-PT)ceramics with large remnant polarization and a narrow optical bandgap.Excellent photovoltaic performance with an ultrahigh open-circuit voltage of 23 V(575 V/cm)is achieved,which is higher than the open-circuit voltages of all reported polycrystalline materials with similar thickness.The phase structure,microstructure morphology,domain structure,ferroelectric and optical characteristics are analyzed,which could provide clues to the origin of the ultrahigh open-circuit voltage of PIMN-PT ceramics.The results suggest that the relaxor-based ferroelectric PIMNPT system is a potential candidate for photovoltaic solar energy conversion devices.

High open-circuit voltage solution-processed organic solar cells based on a star-shaped small molecule end-capped with a new rhodanine derivative

A new star-shaped small molecule named TCNR3TTPA,with a triphenylamine(TPA)unit as the central building block and2-(1,1-dicyanomethylene)-3-octyl rhodanine(CNR)as the end-capped group,has been designed and synthesized.TCNR3TTPA showed a deep highest occupied molecular orbital(HOMO)energy level( 5.60 e V)and broad absorption.The solution-processed bulk heterojunction(BHJ)solar cells based on TCNR3TTPA:PC61BM(1:1,w/w)exhibited a high open-circuit voltage(Voc)of 0.99 V,a short-circuit current density(Jsc)of 5.76 m A/cm2,and a power conversion efficiency(PCE)of 2.50%under the illumination of AM 1.5 G,100 m W/cm2.The high Voc is ascribed to the strong electron-with-drawing ability of the end-capped 2-(1,1-dicyanomethylene)-3-octyl rhodanine group.These results demonstrated that the Voc of small-molecule organic solar cells could be increased by introducing a strong electron-withdrawing end-capped block,and that this is an effective strategy to design high-performance small molecules for organic solar cells.

A new oligobenzodithiophene end-capped with 3-ethyl-rhodanine groups for organic solar cells with high open-circuit voltage

A new solution-processable small-molecule donor material, named DRBDT3, comprised of oligobenzo[l,2-b：4,5-b＇] dithio- phene as the backbone and 3-ethyl-rhodanine as the end-capped group has been designed and synthesized for application in organic photovoltaic cells. The oligobenzodithiophene derivative exhibits an absorption band from 300 to 640 nm. The film of DRBDT3 shows highly long-range ordering assembly and high mobility of 1.21×10^-4 cm^2 V^-1 s^-1. The new molecule shows a deep highest-occupied molecular orbital energy level. The device based on DRBDT3 as the donor and PC71BM as the acceptor exhibits a power conversion efficiency of 4.09% with a high open-circuit voltage of 0.99 V under AM. 1.5G illumination （100 mW cm^-2）.

Enhanced open-circuit voltage in methoxyl substituted benzodithiophene-based polymer solar cells

The open-circuit voltage(V_(oc))is one of the important parameters that influence the power conversion efficiency(PCE)of polymer solar cells.Its value is mainly determined by the energy level offset between the highest occupied molecular orbital(HOMO)of the donor and the lowest unoccupied molecular orbital(LUMO)of the acceptor.Therefore,decreasing the HOMO value of the polymer could lead to a high V_(oc)and thus increasing the cell efficiency.Here we report a facile way to lower the polymer HOMO energy level by using methoxyl substituted-benzodithiophene(BDT)unit.The polymer with the methoxyl functionl group(POBDT(S)-T1)exhibited a HOMO value of-5.65 eV,which is deeper than that(-5.52 eV)of polymer without methoxyl unit(PBDT(S)-T1).As a result,POBDT(S)-T1-based solar cells show a high V_(oc)of 0.98 V and PCE of 9.2%.In contrast,PBDT(S)-T1-based devices show a relatively lower V_(oc)of 0.89 V and a moderate PCE of 7.4%.The results suggest that the involvement of methoxyl group into conjugated copolymers can efficiencly lower their HOMO energy levels.

An effective'salt in dimethyl sulfoxide/water'electrolyte enables high-voltage supercapacitor operated at-50℃

Compared with organic electrolytes,aqueous electrolytes exhibit significantly higher ionic conductivity and possess inherent safety features,showcasing unique advantages in supercapacitors.However,challenges remain for low-salt aqueous electrolytes operating at high voltage and low temperature.Herein,we report a low-salt(0.87 m,m means mol kg^(-1))'salt in dimethyl sulfoxide/water'hybrid electrolyte with non-flammability via hybridizing aqueous electrolyte with an organic co-solvent of dimethyl sulfoxide(hydrogen bond acceptor).As a result,the 0.87 m hybrid electrolyte exhibits enhanced electrochemical stability,a freezing temperature below-50℃,and an outstanding ionic conductivity of 0.52mS cm~(-1)at-50℃.Dimethyl sulfoxide can anchor water molecules through intermolecular hydrogen bond interaction,effectively reinforcing the stability of water in the hybrid electrolyte.Furthermore,the interaction between dimethyl sulfoxide and water molecules diminishes the involvement of water in the generation of ordered ice crystals,finally facilitating the low-temperature performance of the hybrid electrolyte.When paired with the 0.87 m'salt in dimethyl sulfoxide/water'hybrid electrolyte,the symmetric supercapacitor presents a 2.0 V high operating voltage at 25℃,and can operate stably at-50℃.Importantly,the suppressed electrochemical reaction of water at-50℃further leads to the symmetric supercapacitor operated at a higher voltage of 2.6 V.This modification strategy opens an effective avenue to develop low-salt electrolytes for high-voltage and low-temperature aqueous supercapacitors.

Coordinated Capacitor Voltage Balancing Method for Cascaded H-bridge Inverter with Supercapacitor and DC-DC Stage

Cascaded H-bridge inverter(CHBI) with supercapacitors(SCs) and dc-dc stage shows significant promise for medium to high voltage energy storage applications. This paper investigates the voltage balance of capacitors within the CHBI, including both the dc-link capacitors and SCs. Balance control over the dc-link capacitor voltages is realized by the dcdc stage in each submodule(SM), while a hybrid modulation strategy(HMS) is implemented in the H-bridge to balance the SC voltages among the SMs. Meanwhile, the dc-link voltage fluctuations are analyzed under the HMS. A virtual voltage variable is introduced to coordinate the balancing of dc-link capacitor voltages and SC voltages. Compared to the balancing method that solely considers the SC voltages, the presented method reduces the dc-link voltage fluctuations without affecting the voltage balance of SCs. Finally, both simulation and experimental results verify the effectiveness of the presented method.

Challenges in Li-ion battery high-voltage technology and recent advances in high-voltage electrolytes

The electrolyte directly contacts the essential parts of a lithium-ion battery,and as a result,the electrochemical properties of the electrolyte have a significant impact on the voltage platform,charge discharge capacity,energy density,service life,and rate discharge performance.By raising the voltage at the charge/discharge plateau,the energy density of the battery is increased.However,this causes transition metal dissolution,irreversible phase changes of the cathode active material,and parasitic electrolyte oxidation reactions.This article presents an overview of these concerns to provide a clear explanation of the issues involved in the development of electrolytes for high-voltage lithium-ion batteries.Additionally,solidstate electrolytes enable various applications and will likely have an impact on the development of batteries with high energy densities.It is necessary to improve the high-voltage performance of electrolytes by creating solvents with high thermal stabilities and high voltage resistance and additives with superior film forming performance,multifunctional capabilities,and stable lithium salts.To offer suggestions for the future development of high-energy lithium-ion batteries,we conclude by offering our own opinions and insights on the current development of lithium-ion batteries.

Improving open-circuit voltage by a chlorinated polymer donor endows binary organic solar cells efficiencies over 17%

Power conversion efficiency(PCE)of single-junction polymer solar cells(PSCs)has made a remarkable breakthrough recently.Plenty of work was reported to achieve PCEs higher than 16%derived from the PM6:Y6 binary system.To further increase the PCEs of binary OSCs incorporating small molecular acceptor(SMA)Y6,we substituted PM6 with PM7 due to the deeper highest occupied molecular orbital(HOMO)of PM7.Consequently,the PM7:Y6 has achieved PCEs as high as 17.0%by the hotcast method,due to the improved open-circuit voltage(VOC).Compared with PM6,the lower HOMO of PM7 increases the gap between ELUMO-donor and EHOMO-acceptor,which is proportional to VOC.This research provides a high PCE for single-junction binary PSCs,which is meaningful for device fabrication related to PM7 and commercialization of PSCs.

Dynamic Write-Voltage Design and Read-Voltage Optimization for MLC NAND Flash Memory

To mitigate the impact of noise and inter-ference on multi-level-cell(MLC)flash memory with the use of low-density parity-check(LDPC)codes,we propose a dynamic write-voltage design scheme con-sidering the asymmetric property of raw bit error rate(RBER),which can obtain the optimal write voltage by minimizing a cost function.In order to further improve the decoding performance of flash memory,we put forward a low-complexity entropy-based read-voltage optimization scheme,which derives the read voltages by searching for the optimal entropy value via a log-likelihood ratio(LLR)-aware cost function.Simulation results demonstrate the superiority of our proposed dynamic write-voltage design scheme and read-voltage optimization scheme with respect to the existing counterparts.